Normalize MCP Accept handling, add canonical root discovery, bump server version, and expand tests

[Trailgenic]

Motivation

• Improve content negotiation for MCP endpoints so clients that send Accept: application/json, */*, or omit Accept are supported while rejecting unsupported single text/event-stream only requests.
• Expose a canonical MCP discovery payload at the root host and preserve route aliasing for /mcp requests.
• Bump MCP server version metadata and ensure behavior is covered by automated tests.

Description

• Added accept header parsing and normalization logic with acceptMediaTypes, acceptedMcpRequestNeedsNormalization, and normalizedMcpRequest and use a normalized Accept of application/json, text/event-stream when needed in app/mcp/route.ts.
• Updated POST handler to pass the normalized request to handleEllaMcpPost and tightened error messages for invalid Accept/Content-Type combinations.
• Implemented canonical MCP root discovery via isCanonicalMcpRootRequest and discoveryBody to return a JSON discovery payload; added ELLA_* constants from lib/ella-registry into the discovery payload.
• Adjusted CORS/OPTIONS/GET behaviors to return proper Allow headers and 403/405 semantics for non-allowed origins or methods.
• Added MCP_ROOT_HOST and rewrote the root host rewrite in next.config.ts to include ?mcpRoot=1 for the /mcp route.
• Bumped ELLA_MCP_SERVER_INFO.version from 1.1.2 to 1.1.4 in lib/ella-registry.ts and exported additional registry constants consumed by the discovery payload.
• Extended and updated tests/mcp.test.ts with new acceptance negotiation tests, a pingWithHeaders helper, canonical root discovery and alias-preservation tests, and additional assertions against registry constants.

Testing

• Ran the MCP unit tests (tests/mcp.test.ts) under node:test and all tests completed successfully.
• Verified content negotiation scenarios by exercising POST with a variety of Accept headers and asserting responses returned status 200 for supported types and 406/415/403 for invalid combinations.
• Verified canonical root discovery and alias behavior via GET and POST requests to the root host and /mcp alias and asserted discovery payload fields match registry constants.

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Codex Task

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Project	Deployment	Actions	Updated (UTC)
ellaentity	Ready	Preview, Comment	Jul 14, 2026 2:23am